This invention relates to phase-locked magnetron amplifiers and more particularly to circuitry which combines the output power of two magnetron amplifiers each of which are controlled in amplitude and phase. Combining the power of each phase-locked magnetron as in this invention dispenses with the necessity for a high power circulator device which is interposed between the microwave driver input signal and the magnetron output power in an amplifier circuit such as that described in copending U.S. patent application Ser. No. 549,128, now abandoned, and its continuation Ser. No. 750,990, now U.S. Pat. No. 4,571,552, entitled "Phase-Locked Magnetron System" by the same Applicant and assigned to the same assignee as this application. In the circuit of the prior application, a high power ferrite circulator is required when the output power of the magnetron is high. However, the circuit losses in a high power ferrite circulator results in the generation of so much heat that it is impossible to dispose of the heat by passive radiation means in vacuum without destroying the device. The magnetron combiner described in this disclosure can operate in vacuum. Another application where the circuit of this invention may be employed is one in which higher output power is desired than is available from a single magnetron amplifier. Higher output power is obtained by combining two or more magnetron amplifiers to get the sum of their outputs without the need of a higher power circulator.
It is therefore an object of this invention to provide a high power amplifier which is phase controlled and which does not utilize a high power circulator to protect the microwave drive source. It is a feature of this invention that the microwave circuit utilized in achieving the object of this invention allows the power from a plurality of phase and amplitude controlled amplifiers to be summed thereby obtaining a greater power output than can be obtained from the individual amplifiers. It is a further feature of this invention that, because the microwave circuitry does not require a high power circulator, the phase control of the microwave amplifier can be accomplished in a low-power-dissipation environment, such as in satellite applications, where presently available circulators can function.
A specific problem solved by this invention is one relating to the peculiar requirements of the transmitter of a solar-powered satellite. In this application, it is not feasible to use a high power ferrite circulator to protect the driver in a phase-locked, high-gain magnetron directional amplifier circuit because the full power output of the magnetron has to flow through the circulator on its way to the antenna. The circulator must dissipate its loss-generated heat energy by radiation, and the ferrite materials of circulators will not operate at the high temperatures necessary for effective radiation. Under these circumstances, the use of two magnetrons working into a magic T will allow the output power of the magnetrons to flow directly into the antenna without having to go through a circulator. However, the two tubes must be very well matched in phase and amplitude by the circuit of this invention to avoid a large amount of power from being reflected to the driver through the circulator.